What question did this study set out to answer?

This research aims to explore the relationship between short-term indoor CO2 exposure, heart rate, and cognitive performance in university students.

February 26, 2026

Exploring the effects of short-term indoor CO 2 exposure on heart rate and cognition in university students: A pilot study

Key Points

This research aims to explore the relationship between short-term indoor CO2 exposure, heart rate, and cognitive performance in university students.
Conducted a small-N intensive longitudinal design with 54 synchronized observation sets over 6 days.
Tracked heart rate (HR) and cognitive accuracy (ACC) during varying levels of CO2 exposure.
Performed standardized mediation analysis to assess the relationships between the variables.
Heart rate demonstrated a two-stage response to CO2 levels, with initial stability below 1000 ppm and gradual decline as concentrations increased.
Significant mediation effect of HR on cognitive accuracy revealed in higher CO2 conditions (β = 0.389, p = 0.022).
Results indicate CO2 levels over 1000 ppm relate to lowered cognitive performance, emphasizing the need for proper ventilation.

Abstract

Indoor carbon dioxide (CO 2 ) accumulation in university classrooms is associated with fluctuations in students’ cognitive performance. This study investigated the preliminary associations between short-term CO 2 exposure, heart rate (HR), and cognitive accuracy (ACC), leveraging a small-N intensive longitudinal design with 54 synchronized observation sets over 6 days. Results indicated that HR responded to CO 2 in two stages under the observed conditions: an initial sensitive response with relatively stable HR when CO 2 was below the 1000 ppm reference level, followed by a gradual adaptive decline as concentrations increased. Standardized mediation analysis confirmed a global indirect effect (β = −0.106, p < 0.05). Notably, segmented analysis revealed that this physiological-cognitive coupling was primarily driven by the intensified impact of HR on cognitive accuracy in Phase II (β = 0.389, p = 0.022), whereas the mechanism remained exploratory in Phase I. These preliminary findings suggest that the relationship between CO 2 and cognition may be mediated by autonomic regulation (reflected by HR). Under the observed classroom conditions, 1000 ppm may serve as a guideline-aligned environmental reference associated with physiological–cognitive shifts. Practical applications This pilot study suggests that heart rate (HR) mediates the association between indoor CO 2 and cognitive performance in university classrooms. Specifically, CO 2 levels exceeding 1000 ppm were associated with distinct physiological changes and reduced cognitive accuracy, highlighting this value as a critical reference for ventilation control. Practically, these results support implementing occupancy-sensitive ventilation strategies to limit CO 2 accumulation. Additionally, the observed CO 2 -HR coupling indicates that aggregate HR trends derived from wearable devices could serve as non-invasive, supplementary indicators of indoor environmental conditions. These exploratory findings inform future human-centric approaches to indoor environmental quality (IEQ) management in educational settings.

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